Geographical methods for modeling and understanding product usage and operating environment.Understanding how and under what conditions customers use products is critical to making sound engineering design decisions. Traditionally, new generation products are often based on prior designs and test specifications that may or may not subsume sub·sume tr.v. sub·sumed, sub·sum·ing, sub·sumes To classify, include, or incorporate in a more comprehensive category or under a general principle: the range of conditions in a given set of operating environments In computing, an operating environment is the environment in which users run programs, whether in a command line interface, such as in MS-DOS or the Unix shell, or in a graphical user interface, such as in the Macintosh operating system. . This article reviews geographical methods that can aid design engineers in their understanding of what the range of product operating environments will be and the proportion of products that may be in service under a given set of conditions. Ultimately, geographical methods can enable better quantification of the risk involved when making critical design decisions--specifically those decisions related to potentially marginal product In economics, the marginal product or marginal physical product is the extra output produced by one more unit of an input (for instance, the difference in output when a firm's labour is increased from five to six units). function or durability within a certain geographical area. [ILLUSTRATION OMITTED] INTRODUCTION Knowledge of the expected operating environment of a product is needed so that credible product validation tests can be created to confirm that new product designs will meet expected field life needs. During the course of product durability test development, geographical methods and geographic information systems geographic information system (GIS) Computerized system that relates and displays data collected from a geographic entity in the form of a map. The ability of GIS to overlay existing data with new information and display it in colour on a computer screen is used primarily to (GIS) can be used to enable understanding of the whole range of product operating locations, and both the customers and environments associated with those locations. Two examples of how existing data can be analyzed using geographical methods to understand product usage in the presence of a range of environmental operating conditions are presented. The first example discusses the utilization of product warranty return information to determine potential worst case operating locations that later can lead to discovery of the specific conditions that may cause reduced product In model theory, a branch of mathematical logic, the reduced product is a construction that generalizes both direct product and ultraproduct. durability. The second example describes a weighted environmental factor model that was developed to aid in the understanding of automotive air conditioning air conditioning, mechanical process for controlling the humidity, temperature, cleanliness, and circulation of air in buildings and rooms. Indoor air is conditioned and regulated to maintain the temperature-humidity ratio that is most comfortable and healthful. system operating conditions in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. . The weighted model method is presented as an example of how the range of operating conditions can be explored using available, geographically referenced data. HIERARCHY OF PRODUCT USAGE AND ENVIRONMENT Prior to the assessment of a product's operating environment, it is useful to have a simplified model of the potential external factors that will affect a product's function and service life. The parameter diagram, or p-diagram, is a common reliability engineering Reliability engineering is an engineering field, that deals with the study reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time.[1] It is often reported in terms of a probability. tool used to depict a product, the product's function, error states, and external noise factors. The p-diagram (Figure 1) represents a product as a "black box" that takes inputs and performs a function that leads to expected outputs. A simple example product is an automotive headlamp--the headlamp takes in electricity and produces light. In addition to electricity, there are generally other inputs that must be understood before a robust headlamp assembly can be designed and tested. These other inputs are termed noise factors. Noise factors can consist of environmental parameters (i.e., ambient temperature Outside temperature at any given altitude, preferably expressed in degrees centigrade. ), customer usage (i.e., the number of times the headlamps are turned on and off), number of car washes per year, or dimensional variation as a result of the manufacturing process. Products that are not robust to external noises may have lower reliability than expected and could enter an undesirable error state. To augment the p-diagram's ability to represent a product in the face of external factors that may influence durability, a nested hierarchical model In a hierarchical data model, data are organized into a tree-like structure. The structure allows repeating information using parent/child relationships: each parent can have many children but each child only has one parent. (Figure 2) of a product in the real world is proposed that suggests the connectivity of certain factors from the product itself at the lowest level up to a geographical scale at the highest level. Also shown at the far right of the nested hierarchy is "time" to indicate the temporal aspects that exist for nearly every factor affecting product durability. At each layer in the hierarchical model it is likely that existing data for many factors can be located. The most common data needs can often be fulfilled with experimentally collected data or publicly available datasets from government sources. In the United States a wide variety of environmental and demographic data can be obtained at many spatial and temporal resolutions Temporal resolution refers to the precision of a measurement with respect to time. Often there is a tradeoff between temporal resolution of a measurement and its spatial precision (spatial resolution). (addressed in Figure 2) as either small or large entities at fine or course grain that exhibit high or low frequency behaviors. (1) The hierarchical product model is useful towards understanding the levels of measurement where data related to product operating parameters can be found. If a product is known to be sensitive to thermal cycling then it follows that temperature data from both the product itself (component level) and the local ambient temperature (geography level) would be needed to determine how the two temperature values relate. In an automotive environment the ambient temperature and the temperature of a component are often different at any point in time, but frequently there is a relationship between the two values that can potentially be used to model the thermal state of the component under any given ambient condition. Note that the usefulness of a model representing the range of product operating environments is dependent on obtaining georeferenced data at appropriate spatial and temporal scales In snakes, the temporal scales are those scales on the side of the head between the parietals and the supralabials, and behind the postoculars.[1] There are two types of temporal scales:[1]
[FIGURE 1 OMITTED] [FIGURE 2 OMITTED] [FIGURE 3 OMITTED] A BRIEF REVIEW OF GEOGRAPHIC INFORMATION SYSTEMS In the past, it was common to create maps by hand and use layers of transparent vellum vellum: see parchment. or acetate to create overlays that would enable visualization of the relative position of one or many features to another set of features on the ground under various scenarios. Since the late 1980s growth in computing power and intensive software development has led to easy-to-use geographic information systems (GIS) that can subsume, display, and enable analysis of many types of data. A GIS can be described most simply as data linked to a map in a computing environment. On the digital map each type of data is contained in a specific layer (Figure 3). For each point, line segment, or polygon polygon, closed plane figure bounded by straight line segments as sides. A polygon is convex if any two points inside the polygon can be connected by a line segment that does not intersect any side. If a side is intersected, the polygon is called concave. within each layer, a record of data exists that contains details pertaining per·tain intr.v. per·tained, per·tain·ing, per·tains 1. To have reference; relate: evidence that pertains to the accident. 2. to the feature. For line and polygon features the GIS creates topology that describes the relative position and connectivity, if applicable, for each item. Topology enables the creation of networks (i.e., roads, pipelines, electrical grids, etc.) and provides the ability to conduct spatial queries A spatial query is a special type of database query supported by geodatabases. The queries differ from SQL queries in several important ways. Two of the most important are that they allow for the use of geometry data types such as points, lines and polygons and that these queries to find items adjacent or within distance of another feature. [FIGURE 4 OMITTED] Each feature in a GIS normally has additional attribute data. A polygon representing a building might contain the address of the structure, the owner's name, telephone number, square footage, year of construction, etc. A complete layer of all the houses in a city could be displayed along with other layers including streets, political boundaries, cell phone tower locations, sewer lines, shopping malls, flood plains, and more. The design of a GIS enables the user to perform spatial queries between multiple layers of information, such as finding all of the banks within two miles of a specific address or isolating areas where past weather conditions met a combination of user-specified criteria. The subset of features selected by the query will be highlighted in the map and can be further subset if needed. The results of a query can also be exported for use in other software packages. Most GIS packages enable the researcher to display and interact with geographic data Geographic data is about much more than electronic pictures of maps. The geographic data that describes our world allows for city planning, flood prediction and relief, emergency service routing, environmental assessments, wind pattern monitoring and many other applications. in many useful ways. GIS packages enable the user to apply multiple classification methods to quantities or attributes associated with the layers represented on the map. Changing the classification method alters the visual appearance of the items displayed on the map. GIS users should experiment with data classification so that the appropriate representation of the underlying distribution of values is communicated in any paper maps that are created. A sample screenshot See screen shot. from ArcView[TM] 3.2 (2) is shown in Figure 4 to give the reader an example of a "typical" GIS display. In the course of this article, it is not possible to provide a complete review of the capabilities and applications of GIS tools. The reader is strongly encouraged to investigate and evaluate the wide range of GIS software This is a list of notable GIS software applications. See also the comparison of GIS software. Open source software Most widely used open source applications:
APPLICATIONS OF GEOGRAPHICAL METHODS AND GIS Example 1: Geographical Analysis of Field Return Data for a Consumer Product To effectively understand and reduce the risk that external noise factors will affect product function over time normally requires expensive physical testing of prototypes. Before any testing can be performed, a test procedure must be developed that is capable of reproducing expected field failure modes. Many products are improved versions of earlier products that have extensive warranty histories. In the case where there is warranty information available for a product, geographical techniques can be employed to help understand and quantify environmental and customer usage factors that may have led to historic product returns from the field. Coupled with prior knowledge of the sensitivity of a product to varying environmental conditions and customer usage, the results of a geographic analysis of field return data is likely to help point the engineer or researcher toward a set of conditions associated with the locations of highest product return relative to expected returns Expected Return The average of a probability distribution of possible returns, calculated by using the following formula: . The base assumption in this example is that the number of returns is directly proportional (Math.) proportional in the order of the terms; increasing or decreasing together, and with a constant ratio; - opposed to See also: Directly to sales of the product (e.g., if 10% of the total units were sold in a given area, then 10% of the total number of product returns should come from the same area). Where it is discovered that more products were returned than expected, generally, a reason exists for the higher than expected numbers of returns--spatial randomness can be statistically tested to determine the significance of specific problem locations. [FIGURE 5 OMITTED] Given that the locations of both product sales counts and product return counts are known, it is possible to create a series of maps that can lead the researcher to locations where products are returned earlier or in greater proportion than expected based on product sales counts in a given area. The example presented in this article is fictional and was created using available data from the U.S. Census Bureau Noun 1. Census Bureau - the bureau of the Commerce Department responsible for taking the census; provides demographic information and analyses about the population of the United States Bureau of the Census for the Detroit, MI area. The basic, mechanical steps to enable the creation of the maps in Figures 5-7 are listed below: (1) Obtain product sales data by selling location. (2) Obtain returns data by return location origin. It is assumed that the return location is normally the place that the product was used. (This may not be true and should be verified if possible.) (3) Geocode ge·o·code n. The demographic characterization of a neighborhood or locality, especially as used in marketing. locations of sale and returns data. In the case where product sales and returns are made through a set of standardized locations, it is advised to geocode the standard locations separately, in advance of any analysis. Geocoding is a computer process that matches physical addresses with latitude and longitude latitude and longitude Coordinate system by which the position or location of any place on the Earth's surface can be determined and described. Latitude is a measurement of location north or south of the Equator. coordinates. [FIGURE 6 OMITTED] (4) Sum the number of returns for each location. (5) Create a map to visualize the pattern of return counts by location. Often, unusual patterns of product returns can be detected visually at this step (see Figure 5). [FIGURE 7 OMITTED] (6) Create a set of aggregate (group) sales and return locations so that the effect of locations that sell few units is reduced. The level of aggregation should be selected based on appropriate knowledge of how a product behaves in an environment over a selected area. (7) Sum sales and return counts by aggregate geographic area as defined in step (6). (8) Compute chi-squared residual (referred to by Dykes as the signed chi-squared statistic (3)) statistic for the results of step (7). Formula 1: csresidual = (O - E)/[square root of E] where O = observed count of returns E = expected count of returns Positive chi-squared residual values Residual value Usually refers to the value of a lessor's property at the time the lease expires. residual value The price at which a fixed asset is expected to be sold at the end of its useful life. indicate more returns than expected based on sales. Negative values indicate fewer returns than expected. The chi-squared residual statistic is a z-score and the values are normally distributed and centered around zero. The user of the chi-square statistic is advised that the value of the statistic often varies based on the magnitude of the observed or expected values Expected value The weighted average of a probability distribution. Also known as the mean value. with large values of O or E yielding large chi-squared residual values. Conclusions based on small ranges of chi-squared residual values (i.e., -6<csresidual<6) should be made with caution. (9) Map and symbolize chi-squared residual values. Visually review map for "interesting" locations (see Figure 6). (10) Perform local indicators of spatial association Local Indicators of Spatial Association (LISA) Consists of a series of statistics that evaluate the existence of local clusters in the spatial arrangement of a given variable. (LISA The first personal computer to include integrated software and use a graphical interface. Modeled after the Xerox Star and introduced in 1983 by Apple, it was ahead of its time, but never caught on due to its $10,000 price and slow speed. ) (4) analysis of chi-squared residuals to determine the most significant clusters of high or low residuals. High residuals are coupled with locations having conditions to which the product is not robust. Low residual clusters are coupled with locations having favorable operating conditions (see Figure 7). If there are few or no significant clusters and there are many warranty returns, it is possible that the warranty claims are not related to any specific external condition or product duty cycle, but are potentially related to a manufacturing issue. (11) Conduct physical analysis of field returns from both high and low locations. (12)Assess environmental conditions and mechanical or electrical cycling in the locations of high residuals compared to areas of low residual clusters. (13)Select a best set of environmental conditions and cycling profiles needed to perform a physical test. It can be observed from the example maps that there are potentially three main clusters of high residual values indicating potential locations where the product has higher than expected returns. Upon analysis using Anselin's LISA method, (5) as implemented in SpaceStat[TM], the primary cluster of high residuals is located in the upper left of the map. The most significant cluster of high residuals would be the area with the environmental conditions or customer duty cycling that the product was least capable of tolerating. In the scenario illustrated in this example, a test incorporating the conditions and duty cycling of the "worst" area is likely to reproduce the field failure mode in a laboratory setting. Example 2: Population and Time of Vehicle Usage Weighted Model of Temperature and Relative Humidity relative humidity n. The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. for Automotive Applications This example illustrates how weighting of external operating conditions can be used to understand the normal operating envelope of temperature and relative humidity and the points of greatest usage for an automobile, given that both human population and time of human activity are unequally distributed within any given area and time-of-day. Datasets used in the model include Typical Meteorological Year A typical meteorological year (TMY) is a collation of selected weather data for a specific location, generated from a data bank much longer than a year in duration. It is specially selected so that it 'showcases' the range of weather phenomena for the location in question: the (TMY TMY The Midnight Youth (band) 2) data (NREL NREL National Renewable Energy Laboratory NREL Natural Resource Ecology Laboratory (Colorado State University, Fort Collins, CO) ), TMY2 weather station locations (NREL), human population counts by location (U.S. Census), and proportion of vehicular trips by hour of the day (Figures 8-11). (7-9) The model was constructed first by loading the population counts by county (Figure 8) into the GIS system and then creating an additional layer of points representing the TMY2 weather stations (Figure 9). Next, the population points were assigned to the nearest TMY2 weather station using Thiessen polygons computed by the GIS (Figure 10). A Thiessen polygon represents an area around a point where all of the points within the area are closest to the surrounded point of interest than any other point of interest. Next, the human population counts were summed for each Thiessen polygon and the percent of total human population was computed. The result is a list of human population weighted weather stations. The remaining steps of the weighting process were performed in a database using a sequence of grouping queries and calculations. The final results from the query sequence provide data that can be plotted to show the number of operation hours that will occur per year at each combination of temperature and relative humidity for a vehicle operated a total of 500 hours per year had the vehicle actually lived in every TMY2 weather station location (Figure 12). The plot is useful for visually assessing the combinations of relative humidity and temperature that have the greatest operating time. If the product does not function properly in the peak areas of the condition map, it is possible that customer satisfaction will be affected, subsequently generating warranty claims that will be costly to the producer. [FIGURE 8 OMITTED] [FIGURE 9 OMITTED] [FIGURE 10 OMITTED] [FIGURE 11 OMITTED] Areas of high incidence of the most common conditions can be identified for further analysis and, if additional variables are required, the model can be extended to create what is often known as a suitability map. The suitability map requires that additional variables be rescaled or ranked and then weighted appropriately before including them in the model. Suitability modeling is beyond the scope of this article. [FIGURE 12 OMITTED] CONCLUSION Geographical analysis methods are very powerful in their ability to help identify potential locations of good or bad product performance that otherwise might be invisible to the researcher employing nonspatial analysis of data. A GIS is a convenient and powerful tool that can be used to implement geographical methods and enable visual display and dynamic interaction of analysis results. Many different GIS packages are available to the researcher. Many spatial analysis (Data West Research Agency definition: see GIS glossary.) Analytical techniques to determine the spatial distribution of a variable, the relationship between the spatial distribution of variables, and the association of the variables of an area. tools are available in advanced statistics software programs and GIS packages. By analyzing past product warranty history, it is possible to more fully understand the conditions and customer usage parameters that could lead to useful laboratory tests that will enable prediction of a product's service life. References (1) Ahl, V. and Allen, T.F.H., Hierarchy Theory, Columbia University Press Columbia University Press is an academic press based in New York City and affiliated with Columbia University. It is currently directed by James D. Jordan (2004-present) and publishes titles in the humanities and sciences, including the fields of literary and cultural studies, , New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of , 1996. (2) Environmental Systems Research Institute (ESRI (Environmental Systems Research Institute, Inc., Redlands, CA, www.esri.com) The world's leading developer of geographic information systems (GIS) software, including programs that plot ZIP codes and addresses, demographic information and detailed, color-coded data. ), ArcView 3.2, 1999. http://www.esri.com. (3) Dykes, J. and Unwin, D., Maps of the Census: A Rough Guide, Department of Geography, University of Leicester History The University was founded as Leicestershire and Rutland College in 1918. The site for the University was donated by a local textile manufacturer, Thomas Fielding Johnson, in order to create a living memorial for those who lost their lives in World War I. , United Kingdom, 1998. http://www.geog.le.ac.uk/jad7/AGOCG/. (4) Anselin, L., Local Indicators of Spatial Association: LISA, Geographical Analysis, Ohio State University Press The Ohio State University Press, founded in 1957, is a university press and a part of The Ohio State University. External links
The Ohio State University , Columbus, OH, 27:93-115, 1995. (5) Anselin, L., SpaceStat 1.90, Ann Arbor Ann Arbor, city (1990 pop. 109,592), seat of Washtenaw co., S Mich., on the Huron River; inc. 1851. It is a research and educational center, with a large number of government and industrial research and development firms, many in high-technology fields such as , MI (1998). (6) Environmental Systems Research Institute (ESRI), USA Population by County, 1999. http://www.esri.com. (7) National Renewable Energy Laboratory The National Renewable Energy Laboratory (NREL), located in Golden, Colorado, as part of the U.S. Department of Energy, is the United States' primary laboratory for renewable energy and energy efficiency research and development. , TMY2 User's Manual, 1995. http://rredc.nrel.gov/solar/old_data/nsrdb/tmy2/. (8) Federal Highway Administration The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two "programs," The Federal-aid Highway Program and the Federal Lands Highway , Nationwide Personal Transportation Survey, 1995. http://www-cta.ornl.gov/npts/1995/Doc/index.shtml. (9) U.S. Dept. of Energy, Typical Meteorological Year Data (TMY2), 1995. http://www.eren.doe.gov/buildings/energy_tools/energyplus/energyplus_weatherdata.html. by Graham S. Duthie Visteon Corp.* As published in Service Life Prediction: Challenging the Status Quo [Latin, The existing state of things at any given date.] Status quo ante bellum means the state of things before the war. The status quo to be preserved by a preliminary injunction is the last actual, peaceable, uncontested status which preceded the pending controversy. , by the Federation of Societies for Coatings Technology, Blue Bell, PA; ISBN ISBN abbr. International Standard Book Number ISBN International Standard Book Number ISBN n abbr (= International Standard Book Number) → ISBN m 0-934010-60-9, 2005. *Visteon Corporation, One Village Center Dr., Van Buren Township may refer to:
|
|
||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion